This application is a continuation-in-part of the international application PCT/DE93/01223 designating the United States, filed Dec. 16, 1993.
The invention relates to valve gear for one or more overhead valves in an internal combustion engine, especially for the throttle-free load control of Otto-cycle engines, wherein the feeding of the mixture is performed by controlling the lift height and open time of the intake valves.
The invention represents an improvement over the apparatus described in the international application PCT/DE93/01223, the disclosure of which is incorporated herein by reference. This application discloses two camshafts acting on followers on respective connecting levers to control the opening and closing of one or more overhead valves which are spring biased in the closing direction, one of the camshafts controlling the opening and the other controlling the closing. By changing the relative timing of the camshafts, the lift and dwell of the valves can be varied widely.
In the apparatus disclosed in PCT/DE93/01223, one of the levers controlling each valve is a drag lever pivoted about a fixed fulcrum and carrying a follower acted on by one of the camshafts. The other lever controlling each valve is a rocker lever which is pivotably mounted on a fulcrum fixed to the drag lever, one end of the rocker carrying a follower acted on by the other of the camshafts, the other end acting on the valve stem. All of the valve operating components are situated on one side of the axis of the overhead valve as well as far away laterally from this axis, so that the valve train takes a lot of lateral space.
U.S. Pat. No. 4,714,057 discloses a system for the variable valve control for an internal combustion piston engine. In this case one of the shafts bears a conventional cam with opening and closing flanks, and the other shaft bears a cam for the advanced reduction of the closing movement of the valve. This patent discloses a phasing device for changing the relative timing of the two camshafts. Phasing devices are also disclosed in DE 29 09 803 and DE 35 31 000.